Absorbent products such as diapers, sanitary napkins and the like generally include a liquid permeable cover on one surface which may be fabric or apertured film. The purpose of the cover is to structurally contain the loosely packed absorbent material which comprises the bulk of the absorbent product, and to protect the body from direct contact with the absorbent material. The cover is preferably nonabsorbent so that the surface of the cover maintains a dry feel while fluids pass through the cover into the absorbent core. Since the cover material is in direct contact with the body, it should be smooth, soft and comfortable to the touch. Certain visual characteristics such as color, lustre, and texture are also important to consumer acceptance and satisfaction.
Apertured films of polypropylene and polyethylene have been widely used as cover materials for absorbent products since these films are inexpensive, nonabsorbent and readily produced. A particularly preferred material for use as a cover is a coextruded film of polyethylene and ethylene vinyl acetate (EVA) as described in U.S. Pat. No. 4,690,679. The polyethylene side of the film which is used as the body contact side, has a higher melting point than the EVA side of the film which permits the film to be thermally bonded while maintaining structural integrity. The outer polyethylene component of the film may be delustred with calcium carbonate while the EVA component may be pigmented with TiO.sub.2 to increase the opacity of the film.
The polyethylene, coextruded polyethylene/EVA or other polymeric film is impervious to liquids as produced, and must be perforated or otherwise apertured for use as a liquid permeable cover material. The film may be perforated by known methods such as needle punching, pin perforating, embossing and stretching, or roll forming as disclosed in U.S. Pat. No. 4,690,679. Alternatively, the film may be extruded with a solid particulate component which is subsequently removed from the film by stretching and/or mechanical or chemical means. These and other methods may be utilized to produce an apertured, liquid permeable film for use as a cover material on absorbent products.
Apertured films as produced by the aforementioned methods have the desired liquid permeability and other functional properties, but are often lacking in aesthetics. In particular, these films may retain the "plastic" feel characteristic of polymeric films, and may be sticky or uncomfortable in contact with the skin of the user. Moreover, some methods of perforation may impart a certain degree of roughness to the surface of the film which further decreases comfort and consumer acceptance. In this regard, certain nonabsorbent but liquid permeable woven and nonwoven fabrics have superior softness and comfort as compared to apertured films.
It is accordingly an object of the present invention to provide a film having improved softness and hand with certain textile like properties. It is a further object of this invention to provide an apertured film having improved comfort and consumer acceptance when used as the liquid permeable cover on absorbent products. It is a yet further object of this invention to provide a method and apparatus for modifying apertured film in order to enhance the texture and physical properties thereof. These and other objects of this invention will be apparent from the ensuing description and claims.